Got an issue with the latest version of PRO, 5.2.4 that I can confirm doesn’t happen when I rollback to 5.2.3.
Uncaught TypeError: Cannot read property 'length' of undefined
It’s a single flexible content field with a heap of different configurations inside it.
I tried deleting flex fields out of it, and it seems to eventually work again when I delete a certain number of overall fields. That seems to be the only consistent factor, as I’ve tried isolating heaps of different fields to see what happens.
If you like I can send you an export of this field set if that helps – where should I send it?